True balancing for Li-ion batteries?

XTAR Light

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An article about true balancing for Li-ion batteries was published on BatteryTech Online:
https://www.batterytechonline.com/battery-management-systems/active-balancing-innovation-maximizes-li-ion-battery-potential
https://www.truebalancing.com/
Out-of-balance conditions occur in batteries that have multiple cells connected in series. In an out-of-balance battery, the cells are at different states of charge (SOCs). As there is no perfect battery pack of all cells with identical capacities and SOCs, it tends to drift out of balance over time and use. The article introduced the true balancing technology that could balance a battery pack by moving energy from cell to cell within the battery pack, just requiring a modification to the existing BMS.

And it showed a number of benefits to use true balancing in a design. Such as, maximizing the available capacity of the battery, maximizing the battery life. It seems that it will have a lot of benefits for ebikes, EVs. Do you think this technology will be promising? Thanks for your kind comments.
 

turbodog

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No.

Mass produced batteries are close enough in capacity that you can do a charge/discharge cycle without any one cell being over-discharged.

Cell capacity can be further rendered moot by simply matching cells before the pack is assembled.
 
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KITROBASKIN

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Very Interesting. Thank you XTAR Light for the link. If accurate, this would allow Tier 2 batteries to be more useful for consumers. While this tech is being described as economical, it does look like every cell in a pack/module will be wired for voltage check and energy delivery. I recently purchased a used LFP battery pack (https://batteryhookup.com/products/super-beast-module-with-48-headway-38120-hp-3-2v-8ah-24v)
and have to tell you, the BMS wiring looked not just passive, but downright crude. The Headway cells in the pack are labelled as about 2 years old. My plan is to occasionally check pairs of (nominal 3.2V each) batteries but then if imbalances show up, need to figure out how to give them a 'boost'. This True Balance system would be automatic but more labor to assemble and quality control, right?
 

turbodog

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And if the article's premise of out-of-balance-cells is so important... then you need a BMS lead on each and every cell, something's that not gonna happen.

This is an area where theory collides w/ real world and comes up short.
 

jtr1962

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Very Interesting. Thank you XTAR Light for the link. If accurate, this would allow Tier 2 batteries to be more useful for consumers. While this tech is being described as economical, it does look like every cell in a pack/module will be wired for voltage check and energy delivery. I recently purchased a used LFP battery pack (https://batteryhookup.com/products/super-beast-module-with-48-headway-38120-hp-3-2v-8ah-24v)
and have to tell you, the BMS wiring looked not just passive, but downright crude. The Headway cells in the pack are labelled as about 2 years old. My plan is to occasionally check pairs of (nominal 3.2V each) batteries but then if imbalances show up, need to figure out how to give them a 'boost'. This True Balance system would be automatic but more labor to assemble and quality control, right?
I've actually read recently that some people are running 4 series, even 8 series, LFP packs without any sort of balancing circuitry. The secret seems to be to discharge the cells until they sit at 2.5V with no load on them. You then assemble them into a pack. After that you keep the battery between 10% and 90% SOC all the time. You can do the former by never letting the pack drop below 3V per cell, and the latter by doing the absorb/trickle phase of recharging at around 3.4V per cell. You'll never get past 90% or so SOC if you stay at 3.4V per cell.

I imagine something similar might work for regular li-ion, except the numbers would be different. I don't know of anyone that actually tried it.
 

KITROBASKIN

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There are also higher voltage Satiator chargers as well that can be programmed to terminate the charging cycle at, say 80%. Thanks to this thread, thinking about our supplemental battery pack, turns out I Am able to check each cell's voltage. Each of the 8 parallel bundles of six is really close in voltage, and the difference between lowest and highest of all 48 cells is around two hundredths of a volt.

The 12 (3P 4S) Absorbed Glass Mat golf cart sized batteries of our home system have much more variation in voltage. When lightning took out our Outback invertor, I kluged a Xantrex 600 watt inverter to run our son's aquarium, Viasat satellite internet connectivity, fan, and charging duties. (Flashlights came in very handy). Since our system is 24V, I used 2 of the 12 home batteries to give 12V that the inverter required. This created a depression of voltage on the two batteries used, and excess voltage on the other 2 batteries in series. I moved the load around to the higher resting voltage batteries every day or two until putting in a new Outback home inverter. Hoping this did not shorten battery life. I will continue to monitor each 6V battery every couple months.

Expecting on Monday I will order a Victron inverter for this system. We already have a Victron charge controller and two 175 Watt solar panels, with fuses and cable on hand. Curiously, the 15 year old solar rack (Unirac) on our roof requires panel mounting clamps that are a challenge to acquire...

One can imagine a robotic fabrication process that can perform the task of connecting balance leads on each cell. The EV market will decide if the increased complexity and expense will be worth extending the life of battery packs with this (off-the-shelf parts) technology.

Looking forward to hearing other CPF member comments.
 
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